Image sensor units that generate images of a subject to be read such as printed matter are presently known. Image sensor units incorporated in devices such as copy machines, multi-function printers, facsimiles, and scanners are used. Internally, image sensor units typically include a light source, a light guide, a lens, a line sensor, and the like.
Here, when the position of a light guide inside the image sensor unit deviates, an image of the subject to be read cannot be accurately generated. Therefore, there is a demand for light guides to be held firmly inside the image sensor unit. For example, Patent Literature 1 discloses a method of providing a holder in addition to a cover and a frame, and of holding a light guide with this holder.